Electrographic recording process and apparatus employing synchronized recording pulses

ABSTRACT

An improved electrographic recording process and apparatus are provided wherein a recording medium is arranged between two spaced opposed electrodes, one of which is in contact with one side of the recording medium, and the other of which is a recording electrode that indirectly contacts the opposite side of the recording medium through an electrically conductive, magnetically attractable toner powder. Such toner is drawn into a recording region between the recording electrode and the recording medium by an alternating magnetic field, and an electrical record signal of short duration is applied to one of the electrodes at such time that the alignment of the toner in the recording region is at an optimum for providing toner deposition on the recording medium.

United States Patent H91 [111 3,914,771

Lunde et al. Oct. 21, 1975 [54] ELECTROGRAPHIC RECORDING PROCESS3,793,638 2/1974 Weiss et al. 346/74 ES AND APPARATUS EMPLOYINGSYNCHRONIZED RECORDING PULSES Primary Examiner-Bernard Komck AssistantExaminerlay P. Lucas [75] Inventors: George Lunde white Bear Lake;Attorney, Agent, or FirmAlexander, Sell, Steldt &

Stan J. Opseth, Lakeland, both of Minn DeLaHunt [73] Assignee: MinnesotaMining & Manufacturing B CT p y Saint Paul, Minn- An improvedelectrographic recording process and ap- [22] Filed; No 14, 1973 paratusare provided wherein a recording medium is arranged between two spacedopposed electrodes, one of which is in contact with one side of therecording medium, and the other of which is a recording elec- 211 Appl.No.1 415,623

52 us. Cl 346/74 ES' 346/74 E that indirectly contacts the Side of 51Int. c|.'- .cbso 15/06 ewding medium through electrically COMM/five [58]Field of Search 5 45 C 74 ES magnetically attractable toner powder. Suchtoner is 346/74 S 74 SB; 178/6'6 A drawn into a recording region betweenthe recording electrode and the recording medium by an alternating [56]References Cited magnetic field, and an electrical record signal ofshort duration is applied to one of the electrodes at such UNITED STATESPATENTS time that the alignment of the toner in the recording 3,219,014ll/l965 Mott 346/74 ES region is at an optimum for providing tonerdeposition on the recording medium.

3,550,153 12/1970 Haeberle 3,733.6l3 5/1973 Koch 3,7865 I5 l/l974 Walker346/74 ES 21 Claims, 8 Drawing Figures PULSE (ONT/FOL C/PCU/ 7' llllllU.S. Patent Oct. 21, 1975 Sheet2 0f4 3,914,771

FIG. 4

US. Patent Oct. 21, 1975 Sheet30f4 3,914,771

FIG. 5

ELECT/P005 C YL/NDER //VPU T 5 7465 l l l U.S. Patent Oct. 21, 1975Sheet4 0f4 3,914,771

1 ELECTROGRAPHIC RECORDING PROCESS ANIY I APPARATUS EMPLOY-INGSYNCHRONIZED Y RECORDING PULSES BACKGROUND or THE INVENTIONHI.

recording toner images on a recording medium. I It) RELATED; PATENTAPPLICATION vA recording system to which the present invention isrelated is di-sclosed; in copending U.S. Pat. application, Ser. No.353,139 filed Apr. 20, 1973, and includesa "l recording electrode thatis pulsed with a voltage potential to produce a deposition oftonerpowder on a recording medium. In oneembodimentof such system, therecording electrode is located on. the same side of the recording mediumas the toner,*bu-t no method for transporting the toner to the recordingelectrode is shown for that embodiment. One method for transporting thetoner to the recording electrode of such a system would be the use of arotating permanentmagnet that produce a periodiccyclic attraction forthetoner. However, a rotatingi magnet assembly has the deficiency thatthe amount and alignment of toner in the recording region would varybetween minimum and maximum levels as a result of the cyclic magneticforce.

Variation in the level of toner in'thefrecording region, as well as thedirection of the toner chains therein, may give rise to yariation's intha amount of toner transferred to the recording medium during therecprding process and, thus, inhibit the recording of toner images '35at consistent and high quality levels of density and resolution. d Thepresent invention provides an improved method for electrographicrecording to producehigh quality toner images on a recording medium athigh speeds in a reliable, repeatable fashion with substantially novariation in the amount of toner transferred to the recording medium.

SUMMARY OF TI-IEQINVENTION The present invention resides in a processand apparatus for improved electrographic recording of toner images on arecording medium. The apparatus of the present invention includes spacedopposed first and second electrode means with a recording regiontherebetween, a passive recording medium disposed in the recordingregion with a first surface in electronic contactwith the secondelectrode means, an electronically conductive,'magnetically attractabletoner powinvention involves drawing the magnetically attractable tonerinto the recording region by the cyclic' magnetic force and applying thevoltage potential pulses provided by theelectronic circuitry to. one oftheelectrode means when the amount and alignment of toner in therecording region is at an optimum condition for forrnder that is drawninto the recording region by acyclic ing'aehigh densitydeposition oftoner powder in the formof toner images on the recording medium.

In a preferred embodiment the first electrode means -:is mounted on anouter shell of a developer roll that in- .cludejsw an inner rotatingmagnet rotor formed with a plurality of magnet sectors. An indicatordisk is coaxially mounted with the developer roll and rotates incorrespondence with the rotation of the magnet rotor.

Sensing means are associated with the indicator disk' for sensing therotation of the indicator disk and supplyinga signal to the electroniccircuitry that furnishes the voltage; potential pulses to one of thefirst and second electrode means. The rotation of the indicator disk andthe magnet rotor are synchronized such that the signal to the electroniccircuitry causes the potential pulses to be supplied by the electroniccircuitry whenthe first electrode means is substantially aligned withthe radial axis of one of the magnet sectors forming the magnet rotor.

In a modified embodiment, the first electrode means is formed of aplurality of magnetically permeable elec trodes protruding from theshell of the developer roll, and'the magnet sectors forming the magnetrotor in- -duce'a magneticfield of relatively high intensity in eachassembly with alternatingfNorthj and South poles region. Because of suchconcentration, there is an area around each electrode that is void oftoner, and also there is an isolation of the toner on each electrodefrom that on the other electrodes. Accordingly, consistent and highquality recording of tonerimages is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. -I is a diagrammatic side view ofan electrographic recording system incorporating the present inve'ntionyFIG. 2 is a plan view of the system of FIG. 1;

FIG. 3 is a fragmentary, diagrammatic side view showingthe alignment oftoner particle chains on the periphery of a developer roll included inthe system of FIG. 1;

FIG. 4 is a diagrammatic side view showing the manner in which tonerchains on the developer roll of F IG. 3 bridge between the developerroll and a recording member at certain instances of time;

' FIG. 5 is a side view illustrating the alignment of the toner chainson the developer roll of FIG. 3 at other instances of time;

FIG. 6 is a block diagram of theelectronic circuitry employed inthe'present invention;

FIG. 7 is a fragmentary view of the developer roll of FIG. 3 showing anarray of recording electrodes mounted thereon; and

FIG. 8 is a diagrammatic view showing a plurality of the electrodes ofFIG. 7 and toner chains bridging between such electrodes and therecording member of FIG. 4.

"DESCRIPTION OF THE PREFERRED EMBODIMENT 7 Referring now to the drawingsand with specific reference to the diagrammatic views of both FIGS. 1and '2,=there is shown a system that represents a preferred embodimentof the present invention for the electro- P igraphic recording of tonerimages on a recording medium. Included in this electrographic system area toner powder reservoir 1, a cylindrical developer roll 2 and arotatable recording member 3.

The developerroll 2 preferably is of the type disclosed in Anderson,U.S. Pat. No. 3,455,276 and has an inner magnet rotor Sand an outercylindrical shell 6 characterized by low magnetic permeability and lowelectrical conductivity. The magnet rotor includes a cylindrical, magnetsupport core 7 and a plurality of permanent magnet sectors 8 arrangedabout and extending parallel to the cylindrical surface of the supportcore 7 to define a cylindrical peripheral surface having alternatingNorth and South magnetic poles. The developer roll 2 is disposed on anaxle 9 and is constructed in such fashion that the support core 7 andthe magnet rotor 5 rotate in a clockwise direction, whereas the outershell 6 is spaced from the magnet rotor S and preferably is fixed inposition. However, if desired, the outer shell 6 may be driven torotate, but such rotation must be at a speed or in a direction thatdiffers from the rotation of the support core 7. Arranged along a linethat is parallel to the axis of axle 9 are a plurality of individual,spaced apart recording electrodes 10 (only one of which is shown inFIG. 1) that are disposed in the exterior surface of the shell 6 to liesubstantially flush with such surface and define a first electrodemeans. The electrodes 10 are normally utilized to serve as a printingelectrode matrix and each electrode 10 prints a dot, the definition ofwhich is defined by its shape, density and distribution of density. Forpurposes of illustration the size of the electrodes 10 is enlarged inthe drawings. Under normal conditions at least 200 electrodes per inchare disposed on the developer roll 2.

The recording member 3 is mounted on an axle 11 parallel to the axle 9of the developer roll 2 and is preferably rotatably driven clockwise torotate in the same direction as the magnet rotor 5 of the roll 2. Therecording member 3 is formed of an electronically conductive cylindricalelectrode 12 andan endless recording medium 13. The electrode 12 servesas a second electrode means and is positioned in a spaced opposedrelationship with the electrodes 10 to define a recording region 14therebetween. The electrode 12 also serves as a support means for therecording medium 13, which preferably is formed from an anodizedaluminum, overlaid or coated on the periphery of the electrode l2 and isin electronic contact therewith. The term electronic contact is hereindefined as that contact between two materials wherein the chargetransport across the interface of the two materials is determined solelyby the electronic properties of the two materials and not by otherintervening or surrounding materials.

The endless construction of the recording medium 13 is particularlyadapted for use in a display and viewing device. As previously recordedinformation on the medium l3 enters the recording region, such data canbe erased by the electrodes 10 and new data recorded thereon where theold data existed, without any merging of the two. Use of an anodizedaluminum recording medium 13, however, is not essential, nor must themedium 13 be fixed to the support cylinder. Instead a wide variety ofmaterials may be employed to form the medium 13, including the use of apaper tape web that is fed through the recording region 14 Such a webcould be coated on one side with a conductive. material, that wouldcontact the cylindrical electrode 12 and, thus, serves as the secondelectrode means. However, the recording medium 13 should have a lowerlimit of volume resistivity of 10 ohm-cm, and a relatively smoothnontacky surface.

. The toner powder reservoir 1 is tilled with a magneticallyattractable, electronically conducting toner powder l5, such asdisclosed in Nelson, U.S. Pat. No. 3,639,245. The reservoir 1 includes adoctor blade 16 that extends in an axial direction with the roll 2 butis spaced therefrom, to meter the toner 15 in an even 2 layer onto theouter shell 6 of the developer roll 2. The toner 15 is held on theperiphery of outer shell 6 by the magnetic fields of the magnet sectors8 and becomes arranged in the form of toner particle chains 17, asindicated most clearly in FIG. 3. The toner chains 17 align themselveswith the magnetic flux lines of force of the magnet sectors 8. Due tothe rotation of the magnet sectors 8 and the alternating disposition ofthe North and South magnetic poles thereof, the magnetic lines of forceproduced by the sectors 8 vary the alignment of each toner chain 17 insuch fashion that the chains 17 fluctuate between lying adjacent to thesurface of the shell 6 and protruding's'traight out therefrom. In thisway, the toner chains 17 tumble about the periphery of the shell 6 in acounterclockwise direction at a rate not greater than the rotation ofthe magnet sectors 8.

' The toner chains 17 are transported on the developer roll 2 throughthe recording region 14 and end portions of certain of the toner chains17 physically contact the recording medium 13. Deposition of'th'eportions of the toner chains 17 in contact with the recording medium 13and one of the electrodes 10 occurs when a sufficient recording voltagepotential is applied to either the electrode 10 or the cylindricalelectrode 12 and the other is grounded to produce a voltage potentialtherebetween. Such voltage potential produces an electrostatic fieldthat acts as a force pattern b'f-intelligence for exerting a force onthe portions of the toner chains 17 contacting the medium 13, whichforce opposes the magnetic attraction of the magnet sectors 8 for thetoner 15 to produce a deposition of the toner 15 on the medium 13, asdescribed in detail in U.S. Pat. application Ser. No. 353,139 filed Apr.2?), 1973, and naming Arthur R. Kotz as inventor, which application isincorporated herein by reference. The function of the recording medium13 is to support the electrostatic field developed between thecylindrical electrode 12 and the portions of the toner in contact withth'e recording medium 13 when they are at differing voltages. Thedominant electrical characteristic of the medium 13 is its volumeresistivity, which may be nonlinear or polarity sensitive such as inphotoconductors or semiconductors, Volume resistivity of the recordingmedium 13 must be of such value to produce an electrostatic fieldsufficient to deposit a required amount of toner on the medium 13. Ingeneral, as previously mentioned, a volume resistivity of 10".ohm-cm orgreater is sufficient, but in no event should the volume resistivity beof such magnitude that thereis not some current flow between theelectrode 12 and the toner deposited on the medium, 13 to relax theelectrostatic force. holding the toner on the medium 13 so that thetoner can be subsequently erased from the medium 13 upon reentering therecording region 14.

Although the present invention encompasses the basic electrographicrecording process taught by Kotz, the present invention adds a newdimension to the teachings of Kotz, which did not involve a rotatingmagnet rotor and set out no definite criteria for timing the applicationof record voltage potential pulses to produce optimum toner depositionson the recording medium 13. Applicants have found that the cyclic natureof the magnetic fields of force urging the toner chains 17 around theperiphery of the developer roll 2 produces cyclic changes in theeffective conductivity of the electrical path from the electrodes to therecording medium 13 because of the constantly changing alignment of thetoner chains 17 in the recording region 14. At times the toner chains 17in the recording region 14 bridge between the periphery of the developerroll 2 and the medium 13 to provide conductive paths of relatively highconductivity between the electrodes 10 and the medium 13. At othertimes, the chains 17 in the recording region 14 bridge from one point ofthe developer roll 2 to another point thereon so that relatively lowconductive paths result. The effective conductivity provided by thetoner 15 in the recording region 14 because of bridging of the tonerchains 17 between the electrodes 10 and the medium 13 is at a maximumwhen the electrodes 10 are substantially in line with the radial axis ofone of the magnet sectors 8, as shown in FIG. 4. In contrast, nulls inthe effective conductivity provided by the toner powder 15 in therecording region 14 due to bridging of the toner chains 17 between twopoints of the developer roll 2 occur when the electrodes 10 are alignedwith the interface between adjacent sectors 8, as indicated in FIG. 5.

The present invention utilizes the variations in the effectiveconductivity and alignment of the toner chains 17 in the recordingregion 14 by synchronizing the application of record voltage potentialspulses to either the electrodes 10 or the cylindrical electrode 12 withthe rotation of the developer roll magnet rotor 5 such that each pulseis applied when the effective conductivity of toner chains 17 bridgebetween the developer roll 2 and the recording medium 13 is at amaximum. In this way, a dense distinct pattern of the toner 15 isdeposited on the medium 13. Furthermore, optimum deposition of the toner15 is achieved with little variation in the amount of toner transferredto the recording me dium 13 during each recording cycle.

Referring again now to FIGS. 1 and 2, synchronization between therotation of the magnet rotor 5 and the application of the recordingvoltage potential pulses is furnished by an indicator disk 22, a sensingmeans which may take the form of a light emitting diode 23 and aphotosensing device 24 (shown only in FIG. 2),

and an electrode pulse control circuit 25. The indicator disk 22 ismounted on the axle 9 for the developer roll 2 and rotates incorrespondence to the magnet rotor 5. The disk 22 is arranged with aperipheral portion between the light emitting diode 23 and thephotosensing device 24. The peripheral portion of the disk 22 hasalternate opaque and translucent panels 26 and 27 respectively, so thelight emitted from the diode 23 is alposition with respect to theelectrodes 10 for recording. When the circuit 25 receives this indicatorsignal together with a record pulse signal from one of a plurality ofdata input lines 29, the circuit 25 supplies a voltage potential recordpulse on a line 30 to the electrode 10 corresponding to the data inputline 29 from which the data pulse is received. There is an input line 29and a corresponding output line 30 for each electrode 10. By applyingcontrolled pulse width voltage record potentials to various of theelectrodes 10 while one of the I magnet sectors 8 is in an optimumposition for recording, repeatably dense well defined dots are recordedon the medium 13.

The pulse control circuit 25, as shown in block form in FIG. 6, isformed of an input stage 31 that is actuated by the indicator pulsesignals from the photosensing device 24. The output of the input stage31 is fed to one input of a gating circuit 32 formed of a plurality ofAND gates (not shown) that each receive the signals from the input stage31. Each gate of the circuit 32 also has a second input that connectswith one of the data input lines 29. When signals are received at bothinputs of one of the AND gates forming the circuit 32, a voltagepotential record pulse is furnished to the electrode 10 corresponding tothe triggered AND gate.

Recording is performed in correlation with the indicator pulse signalsproduced by the photosensing device 24. However, each recording pulseneed not be as long as the indicator signal pulses because the inputstage 31 may include circuitry for expanding or narrowing the indicatorpulse signals. A delay network may also form a portion of the inputstage 31 to delay the indicator pulse signals received-from the device24. Therefore, the indicator pulses may be lengthened, shortened ordelayed by the use of proper circuitry in the input stage 31. Anothermethod for obtaining such control is to employ the indicator pulsesignals solely as triggering pulses to actuate a pulse generating devicethat is variable to provide pulses to the gating circuit 32 at theoptimum time for highest quality recording. Such circuitry is old in theart and for purposes of clarity and brevity will not be describedherein.

Referring now to FIG. 7, the concentration of toner particles in therecording region 14 and the preferential alignment of the toner chains17 in the recording region 14 can be improved by substitutingmagnetically permeable electrodes 33, for the electrodes 10. Theelectrodes 33 protrude from the developer roll outer shell 16 and arepartially encapsulated by an insulating material 34 having a lowmagnetic permeability. The outer ends of the electrodes 33- are exposedto come in electronic contact with the toner powder chains 17 that enterthe recording region 14.

The employment of magnetically permeable electrodes 33 increases themagnetic field density in the recording region 14 because the fields ofthe magnet sectors 8 magnetize, or induce a relatively strong magneticfield in the electrodes 33. The magnetic fields induced in theelectrodes 33 cause the magnetic toner chains 17 in the recording region14 to concentrate in the area of highest field strength, which exists atthe outer end of the electrodes 33 and extends out to the surface of therecording medium 13. Due to the magnetic fields induced in theelectrodes 33 there is a region near the electrodes 33 which is void oftoner chains 17 because any toner in that region is attracted to theelectrodes 33. There is also an isolation of the chains of toner 17 oneach electrode 33 from those chains on adjacent electrodes 33 asillustrated by the array of five electrodes in FIG. 8 wherein associatedmagnetized toner chains 17 are shown tending to repel one another and tofollow the lines of magnetic flux emanating from the electrodes 33.

The isolating and concentrating effects produced by the magneticelectrodes 33 on the toner l5 tend to reduce current. flow betweenadjacent electrodes and to increase current flow through the tonerchains 17 to those toner particles in contact with the recording-medium13. Consequently, even though the magnetic force on the toner particlesin contact with the recording medium 13 is greater than that existingwhen nonmagnetic electrodes 10 are used, the amount of toner l5transferred to the recording medium 13 is greater with the magneticelectrodes 33.

Such improved recording is achieved by the use of electrodes 33 becausethere are more toner particles that both contact the recording medium 13and have direct electrical continuity with one of the electrodes 33 dueto the concentrating effect of the toner chains 17. Also, the electricalconductivity through the toner chains 17 bridging between the electrodes33 and recording medium 13 is better (lower resistance) due to highercontact force between the toner particles form-' ing the tonerchains 17.Accordingly, when the electrodes 33 are pulsed with a record voltagepotential pulse fromthe pulse control circuit 25, toner images ofconsistently high quality levels of density and resolution are depositedon the recording medium 13. It has been found that the highestqualityimages are produced when the record voltage potential pulses are begunjust before the toner chains 17 bridging between the electrodes 10 andthe medium 13 are removed from the recording region 14 as a result ofthe rotation of the magnet rotor 5. This occurs as'the radial axis ofone of the magnetic sectors 8 moves past a position ofalignment withtheelectrodes l0.

The following non-limiting example is now provided.

EXAMPLE 1 This example involves use of an apparatus as shown in FIG. 1,modified with the magnetically permeable electrodes 33 of FIG. 8. Theouter shell 6 of the developer roll 2 was constructed of a 2.5 in. innerdiameter linen phenolic tubing, with a 0.094 in. wall thickness. Thediameter of the magnet rotor 5 was 2.470 in., and had 16 magnet sectors8 providing alternating North and South poles around its circumferenceto produce a field strength of approximately 700 gauss on the rotorperiphery. A thin aluminum sleeve was positioned over and cemented tothe magnet sectors 8 to hold them in place at high speeds. Theelectrodes 33 were constructed of 0.070 in. diameter iron music wirewith each 0.120 in. long, and located on O.l40 in. centers ing toNelson, US. Pat. No. 3,639,245 with a static resistivity of lessthan lohm/cm. and-preferably less than ohm/cm. in an applied electric field of1000 v./cm.

The magnet rotor 5-was rotated at 5,800 rpm in a clockwise directioncausing the toner chains 17 to tumble about the peripheral surface ofthe developer roll 2 in a counter clockwise direction. The doctor blade16 was spaced from the developer roll 2 to define approximately a 0.010in. gap to meter an even layer of toner across the exterior surface ofthe shell 6 in 0.060 in.

cordingmember 3 was. 22 in./second and the gap between the recordingmedium 13 and the electrodes 33 was 0.004 in. Torecord, each electrode33 was selectively pulsed by a volt potential and the electrode 12 wasgrounded. For erasing previously recorded toner images the electrodes 33were left at ground potential. The half period'of the magnetic cycle(length of time each pole is under the recording styli) was 670microseconds, and a recording pulse width of approximately 200microseconds was applied at approximately the position at which theunloading of the toner from the electrodes 33 would normally occur if novoltage pulse was applied. I

What is claimed is:

1. An electrographic recording process for the deposition of toner on arecording medium, which process comprises: I

l. arranging first and second electrode means in a spaced opposedrelationship to provide a recording region therebetween;

2. arranging a recording medium in said recording region with a firstsurface in electronic contact with said second electrode means;

3. drawing electronically conductive, magnetically attractable tonerinto the recording region by means of an alternating magnetic field sothat the toner is interposed between said first electrode means and asecond surface of said recording medium to form an electronicallyconductive path therebetween, whereby a portion of said toner is inphysical contact with said second surface of said recording medium; and

4. establishing voltage potential pulses of short duration between saidfirstand second electrode means at such times that the alignment oftoner in the recording region is at an optimum for providing tonerdeposition on the recording medium in response to an electrical forcepattern of intelligence on the portion of said toner in physical contactwith said recording medium and determinedby the electrical potentialdifference established between said'portion'of said toner and'saidsecond electrode means, said electrical force pattern exerting a forceon said portion of said toner which is greater than and in opposition tothe force exerted on said portion by said magnetic field. t

2. A process as recited in claim 1 wherein said voltage potential pulsesare applied to said first electrode means.

3. .A process as recited in claim 1 wherein said first electrode meansis magnetically permeable and said alternating magnetic field induces'amagnetic field move in the same direction relative to said firstelectrode means.

5. A process as recited in claim 1 wherein said first and secondelectrode means are stationary relative to each other and said recordingmedium moves through said recording region.

6. A process as recited in claim 1 wherein said recording medium is aweb.

7. A process as recited in claim 1 wherein said second electrode meanscomprises an electrically conductive cylindrical member.

8. A process as recited in claim 1 wherein said recording medium isbonded to said second electrode means.

9. A process as recited in claim 8 wherein said recording medium isformed of anodized aluminum.

10. A process as recited in claim 1 wherein said first electrode meansis a plurality of electronically conductive, electrically isolatedelectrodes.

11. A process as recited in claim 1 wherein said alternating magneticfield is provided by a developer roll having an outer shell on whichsaid first electrode means is mounted and an inner magnetic rotor with aplurality of magnet sectors to provide alternating North and Southmagnetic poles on its peripheral surface.

12. A process as recited in claim 11 wherein the application of saidvoltage potential pulses is synchronized with the rotation of saidmagnet rotor such that said pulses are applied when said first electrodemeans is substantially aligned with the radial axis of one of saidmagnet sectors of said developer roll.

13. A process as recited in claim 12 wherein indicator means areassociated with said developer roll for providing signals indicative ofthe rotational position of said roll.

14. A process as recited in claim 13 wherein said indicator meanscomprises an indicator disk that is coaxially mounted with saiddeveloper roll and rotates in correspondence with the rotation thereof,and sensing means are employed to sense the position of said indicatordisk.

15. A process as recited in claim 14 wherein electronic circuitryprovides said voltage potential pulses to one of said electrode meansand signals from said sensing means actuate said electronic circuitry.

16. An apparatus for the electrographic recording of toner on arecording medium and comprising:

1. a developing means having an outer shell and inner rotor member thatrotates with respect to said outer shell, said inner rotor member havinga plurality of magnet sectors to provide alternating North and Southmagnetic poles on its circumference;

2. a first electrode means mounted on the outer shell of said developingmeans;

3. a second electrode means in spaced opposed relationship to said firstelectrode means to provide a recording region therebetween;

4. an electronically conductive, magnetically attractable toner powder;

5. toner supply means for supplying said toner powder to said developingmeans, which toner is attracted to the outer shell of said developingmeans by said magnetic poles of said rotor;

. transport means for providing movement of the recording mediumrelative to at least one of said first and second electrode means andthrough said recording region, said toner providing an electronicallyconductive path in said recording region between one surface of saidrecording medium and said first electrode means, said second electrodemeans being in electronic contact with the opposite surface of saidrecording medium;

7. electronic circuitry adapted to apply voltage potential pulses ofshort duration to one of said electrode means; and

8. synchronizing means for monitoring the rotation of the rotor of saiddeveloping means and actuating said electronic circuitry to apply saidpulses to one of said electrodes to establish a voltage differencebetween said electrode means at such time that the amount and alignmentof toner in the recording region is at an optimum for providing tonerdeposition on the recording medium.

17. An apparatus as recited in claim 16 wherein said voltage potentialpulses are applied to said first electrode means.

18. An apparatus as recited in claim 16 wherein said first electrodemeans is magnetically permeable and said alternating magnetic field ofsaid developer roll in duces a magnetic field therein.

19. An apparatus as recited in claim 16 wherein the application of saidvoltage potential pulses is synchronized with the rotation of saidmagnet rotor such that said pulses are applied when said first electrodemeans is substantially aligned with the radial axis of one of saidmagnet sectors of said developer roll.

20. An apparatus as recited in claim 19 wherein an indicator disk iscoaxially mounted with said developer roll and rotates in correspondencewith the rotation thereof, and sensing means are employed to sense therotation of said indicator disk.

21. An apparatus as recited in claim 20 wherein electronic circuitryprovides said voltage potential pulses to one of said electrode meansand signals from said sensing means actuate said electronic circuitry.

1. An electrographic recording process for the deposition of toner on arecording medium, which process comprises:
 1. arranging first and secondelectrode means in a spaced opposed relationship to provide a recordingregion therebetween;
 2. arranging a recording medium in said recordingregion with a first surface in electronic contact with said secondelectrode means;
 3. drawing electronically conductive, magneticallyattractable toner into the recording region by means of an alternatingmagnetic field so that the toner is interposed between said firstelectrode means and a second surface of said recording medium to form anelectronically conductive path therebetween, whereby a portion of saidtoner is in physical contact with said second surface of said recordingmedium; and
 4. establishing voltage potential pulses of short durationbetween said first and second electrode means at such times that thealignment of toner in the recording region is at an optimum forproviding toner deposition on the recording medium in response to anelectrical force pattern of intelligence on the portion of said toner inphysical contact with said recording medium and determined by theelectrical potential difference established between said Portion of saidtoner and said second electrode means, said electrical force patternexerting a force on said portion of said toner which is greater than andin opposition to the force exerted on said portion by said magneticfield.
 2. arranging a recording medium in said recording region with afirst surface in electronic contact with said second electrode means; 2.A process as recited in claim 1 wherein said voltage potential pulsesare applied to said first electrode means.
 2. a first electrode meansmounted on the outer shell of said developing means;
 3. a secondelectrode means in spaced opposed relationship to said first electrodemeans to provide a recording region therebetween;
 3. A process asrecited in claim 1 wherein said first electrode means is magneticallypermeable and said alternating magnetic field induces a magnetic fieldtherein.
 3. drawing electronically conductive, magnetically attractabletoner into the recording region by means of an alternating magneticfield so that the toner is interposed between said first electrode meansand a second surface of said recording medium to form an electronicallyconductive path therebetween, whereby a portion of said toner is inphysical contact with said second surface of said recording medium; and4. establishing voltage potential pulses of short duration between saidfirst and second electrode means at such times that the alignment oftoner in the recording region is at an optimum for providing tonerdeposition on the recording medium in response to an electrical forcepattern of intelligence on the portion of said toner in physical contactwith said recording medium and determined by the electrical potentialdifference established between said Portion of said toner and saidsecond electrode means, said electrical force pattern exerting a forceon said portion of said toner which is greater than and in opposition tothe force exerted on said portion by said magnetic field.
 4. A processas recited in claim 1 wherein said recording medium and said secondelectrode means move in the same direction relative to said firstelectrode means.
 4. an electronically conductive, magneticallyattractable toner powder;
 5. toner supply means for supplying said tonerpowder to said developing means, which toner is attracted to the outershell of said developing means by said magnetic poles of said rotor; 5.A process as recited in claim 1 wherein said first and second electrodemeans are stationary relative to each other and said recording mediummoves through said recording region.
 6. A process as recited in claim 1wherein said recording medium is a web.
 6. transport means for providingmovement of the recording medium relative to at least one of said firstand second electrode means and through said recording region, said tonerproviding an electronically conductive path in said recording regionbetween one surface of said recording medium and said first electrodemeans, said second electrode means being in electronic contact with theopposiTe surface of said recording medium;
 7. electronic circuitryadapted to apply voltage potential pulses of short duration to one ofsaid electrode means; and
 7. A process as recited in claim 1 whereinsaid second electrode means comprises an electrically conductivecylindrical member.
 8. A process as recited in claim 1 wherein saidrecording medium is bonded to said second electrode means. 8.synchronizing means for monitoring the rotation of the rotor of saiddeveloping means and actuating said electronic circuitry to apply saidpulses to one of said electrodes to establish a voltage differencebetween said electrode means at such time that the amount and alignmentof toner in the recording region is at an optimum for providing tonerdeposition on the recording medium.
 9. A process as recited in claim 8wherein said recording medium is formed of anodized aluminum.
 10. Aprocess as recited in claim 1 wherein said first electrode means is aplurality of electronically conductive, electrically isolatedelectrodes.
 11. A process as recited in claim 1 wherein said alternatingmagnetic field is provided by a developer roll having an outer shell onwhich said first electrode means is mounted and an inner magnetic rotorwith a plurality of magnet sectors to provide alternating North andSouth magnetic poles on its peripheral surface.
 12. A process as recitedin claim 11 wherein the application of said voltage potential pulses issynchronized with the rotation of said magnet rotor such that saidpulses are applied when said first electrode means is substantiallyaligned with the radial axis of one of said magnet sectors of saiddeveloper roll.
 13. A process as recited in claim 12 wherein indicatormeans are associated with said developer roll for providing signalsindicative of the rotational position of said roll.
 14. A process asrecited in claim 13 wherein said indicator means comprises an indicatordisk that is coaxially mounted with said developer roll and rotates incorrespondence with the rotation thereof, and sensing means are employedto sense the position of said indicator disk.
 15. A process as recitedin claim 14 wherein electronic circuitry provides said voltage potentialpulses to one of said electrode means and signals from said sensingmeans actuate said electronic circuitry.
 16. An apparatus for theelectrographic recording of toner on a recording medium and comprising:17. An apparatus as recited in claim 16 wherein said voltage potentialpulses are applied to said first electrode means.
 18. An apparatus asrecited in claim 16 wherein said first electrode means is magneticallypermeable and said alternating magnetic field of said developer rollinduces a magnetic field therein.
 19. An apparatus as recited in claim16 wherein the application of said voltage potential pulses issynchronized with the rotation of said magnet rotor such that saidpulses are applied when said first electrode means is substantiallyaligned with the radial axis of one of said magnet sectors of saiddeveloper roll.
 20. An apparatus as recited in claim 19 wherein anindicator disk is coaxially mounted with said developer roll and rotatesin correspondence with the rotation thereof, and sensing means areemployed to sense the rotation of said indicator disk.
 21. An apparatusas recited in claim 20 wherein electronic circuitry provides saidvoltage potential pulses to one of said electrode means and signals fromsaid sensing means actuate said electronic circuitry.